As is known, many pourable food products, such as fruit juice, UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material. The packaging material has a multilayer structure comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material, and which is covered on both sides with layers of thermoplastic material, e.g. polyethylene film. In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material comprises a layer of oxygen-barrier material, e.g. aluminium foil, which is superimposed on a layer of thermoplastic material, and is in turn covered with another layer of thermoplastic material forming the inner face of the package eventually contacting the food product.
Packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating; and the web of packaging material so sterilized is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled with the sterilized or sterile-processed food product, and is sealed and subsequently cut along equally spaced cross sections to form pillow packs, which are then folded mechanically to form respective finished, e.g. substantially parallelepiped-shaped, packages.
Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles, and the packages are filled with the food product and sealed. One example of this type of package is the so-called “gable-top” package known by the trade name Tetra Rex (registered trademark).
Once formed, the above packages may undergo further processing, such as the application of an opening device to enable the product to be poured out.
At present, the most commonly marketed opening devices comprise a frame portion defining a pour opening and fitted about a removable or pierceable portion of a top wall of the package; and a cap hinged or screwed to the frame portion, and which is removable to open the package.
In particular, each opening device may be applied to a corresponding so-called “prelaminated” hole of the packaging material, i.e. a hole formed in the base layer only and covered by the other lamination layers, including the layer of gas-barrier material.
Applying units for applying opening devices to packages are known in which the packages are advanced by a conveying unit, for example a conveyor belt defining a substantially horizontal plane and supporting the packages. The applying units further comprise an applying device having applying elements that receives an opening device from a delivery unit, advance the opening device through a gluing unit, in which a layer of glue is distributed on the frame portion of the opening device, and then apply the opening device to a wall, in particular to a top wall, of the package.
The applying units further comprise a sensor device, for example a camera, which detects the position of the packages, in particular of the “prelaminated” holes, and generates a signal which controls the applying elements.
A drawback of the known applying units is that the opening device may be improperly applied to the package. In particular, in case the package is not aligned with the applying element—for instance in case the package is tilted on the conveyor belt—the opening device is not arranged in the right position, for example is not centered on the “prelaminated” hole. In this way, the final package may be defective.
In case the mutual misalignment of the package and the applying element is even bigger, the applying unit may not be able at all to apply the opening device on the package.